Victoria's efforts to find a fix for the city's iconic but aging blue bridge will hit a crucial turning point this week when city council decides whether the 84-year-old structure should be refurbished or torn down and replaced with a brand new bridge.

Either way, taxpayers will be asked to approve the largest borrowing bylaw in the city's history.

Engineering and economic-impact assessments presented to council in June pegged the cost of rehabilitating the existing Johnson Street Bridge at $80-million, with no guarantee of federal or provincial funding.

Replacing the bridge would cost about $77-million and allow the city to use a $21-million federal infrastructure grant it received last year, reducing the city's borrowing obligation to $56-million, the reports said.

Council's decision Thursday will set the stage for a November referendum in which taxpayers will be asked to approve a borrowing bylaw for the chosen project.

"Whether it's refurbishment or replacement, we do need to make a decision and move forward," said Victoria Mayor Dean Fortin.

"The most important thing is that we put forth a referendum question that has the best chance to succeed … because not doing the bridge is the worst-case scenario."

The city is required by law to maintain a working lift-span that provides maritime access to the Gorge Waterway, which is considered a "working harbour" under Transport Canada's Navigable Waters Act.

Council launched a bid to replace the bridge 18 months ago based on staff reports predicting the structure will suffer a massive failure within five years,

However, opponents of the original plan, which would have required taxpayers to borrow $42-million, collected nearly 10,000 signatures on a counter-petition, well over the 10-per-cent threshold required to force a referendum under B.C. law.

Mr. Fortin said council will base its decision on two public-opinion surveys the city has commissioned. The survey results will be released Wednesday and Thursday.

Mr. Fortin's term as mayor will be largely defined by the outcome of November's vote.

Successive engineering reports have concluded the riveted steel lift-span across Victoria's scenic Gorge Waterway suffers from "pervasive" corrosion and "obsolete" electrical and mechanical systems, and that it would almost certainly collapse in the event of a major earthquake.

City engineering director Mike Lai said if the referendum fails, liability concerns could force an extended closing of the bridge, noting that his department has a legal obligation to address the deficiencies identified in the reports.

Ross Crockford of JohnsonStreetBridge.org, the group that led the counter-petition campaign last fall, accused the city of using scare tactics to persuade residents to borrow millions.

"The whole thing about 'We have to do something or we're going to take the bridge away' is complete bullshit," Mr. Crockford said. "Just because the thing is rusting doesn't mean you have to condemn it."

Mr. Crockford's group wants to see the original structure preserved, including the existing E&N Railway link to downtown, an option that council has rejected, saying it would add between $12-million to $23-million in cost.

Mr. Crockford said the city's public-information campaign has been slanted toward a new bridge and predicted that council will choose the replacement option Thursday.

After a prolonged silence on the issue, the Greater Victoria Chamber of Commerce last week threw its support behind a new bridge, citing lower costs and fewer disruptions to downtown businesses.

Plans call for a replacement bridge to be built alongside the existing bridge, all but eliminating the need for bridge closings during construction, while the refurbishment option would require prolonged closings over a six- to 12-month period.